Adaptive disturbance compensation based finite time sliding mode frequency control considering AVR loop for low-inertia power system

Load frequency control (LFC) and automatic voltage regulator (AVR) demonstrate a weakly coupled relationship, and there remains a lack of research focusing on the analysis of AVR effects on frequency dynamics, particularly in low-inertia environments. This paper presents a theoretical analysis that substantiates the reduction in system stability margin and the occurrence of frequency fluctuations in low-inertia systems due to the inclusion of the AVR. To mitigate fluctuations, a finite-time sliding mode control integrated with disturbance compensation is proposed. The primary objective is to achieve swift frequency stabilization and prevent the generation output from exceeding safety limits caused by singularity problems. To address this, a non-singular finite-time sliding mode controller is developed. Considering the adverse effects of disturbances from renewable energy sources and the load, the compensation of the aggregated disturbance is realized by the disturbance observer. This avoids a large switching gain caused by high disturbance bounds and eliminates chattering. Finally, due to the significant variations in the output of renewable energy sources, the bound of aggregated disturbance is unknown, and an adaptive strategy is proposed to overcome the challenge. The effectiveness has been verified through real-time simulation experiments using RT-Lab.